This post was published long before the Mists of Pandara Expansion.
The tips and techniques explained here may be outdated.

Warlock Spell: Corruption

Here’s my visualization of the spell cast. Above is the timeline. It’s dotted in 1 second intervals with an extra dark dot at each 5 seconds to make it easier to read.

The spell is cast at time 0. The “X” is the Global Cooldown (GCD) (1.5 seconds). The dotted purple/grey lines are where damage actually occurs. Assuming the dot runs for full duration it will do 6 ticks.

Assuming I have 1k bonus shadow damage each tick should hit for ~446 for a total of ~2677.

Relevant Talents:

Improved Corruption 5/5 – Make Corruption instant cast. It’s tempting to take it down to only 1.5 second cast (1.5 second cast, 1.5 second GCD) but that’s only useful if you can stand still and cast. By making it instant you can make it so that you can cast it while at a full run.Empowered Corruption 3/3 – Your Corruption spell gains an additional 36% of your bonus spell damage effect.Contagion 5/5 – Increases the damage of Curse of Agony, Corruption and Seed of Corruption by 5% and reduces the chance your Affliction spells will be dispelled by an additional 30%Nightfall 2/2 – Gives your Corruption or Drain Life spells a 4% chance to cause you to enter a Shadow Trance state after damaging the opponent. The Shadow Trance state reduces the casting time of your next Shadow Bolt 100%.Shadow Embrace 5/5 – Your Corruption, Curse of Agony, Siphon Life and Seed of Corruption spells also cause the Shadow Embrace effect which reduces physical damage cause by 5%.Shadow Mastery 5/5 – Increase the damage dealt or life drained by your Shadow Spells by 10%